One theory is that the summer sun melts ice on the surface of the glacier which creates pools of water which then flow into moulins -- narrow tubular shafts in the glacier.

CNN: Rubber ducks aid NASA study

"But, ' adds Mel Reasoner, Director of the Mountain Research Initiative, "in many arid and semi-arid areas, people are dependent not only on the amount of glacier melt water, but on the timing of the water flow.

UNESCO: 83e

Pyroclastic flow generation, ejection of incandescent material, and tephra fall affected the glacier.

UNESCO: Dublin Core